﻿// Copyright(c) Microsoft Corporation
// All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the License); you may not use
// this file except in compliance with the License. You may obtain a copy of the
// License at http://www.apache.org/licenses/LICENSE-2.0
//
// THIS CODE IS PROVIDED ON AN  *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS
// OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY
// IMPLIED WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
// MERCHANTABILITY OR NON-INFRINGEMENT.
//
// See the Apache Version 2.0 License for specific language governing
// permissions and limitations under the License.

using System;
using System.Threading;

namespace Microsoft.Python.Core.Disposables {
    public sealed class CountdownDisposable {
        private readonly Action _createAction;
        private readonly Action _disposeAction;
        private int _count;
        public int Count => _count;

        public CountdownDisposable(Action disposeAction = null) : this (() => { }, disposeAction) { }
        public CountdownDisposable(Action createAction, Action disposeAction) {
            _createAction = createAction ?? (() => {});
            _disposeAction = disposeAction ?? (() => {});
        }

        public IDisposable Increment() {
            if (Interlocked.Increment(ref _count) == 1) {
                _createAction();
            }

            return Disposable.Create(Decrement);
        }

        public void Decrement() {
            if (Interlocked.Decrement(ref _count) == 0) {
                _disposeAction();
            }
        }
    }
}
